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If your not worried about a decrease in performance get a chrome whale penis and put a big dirty poddy on the end. If you want some extra street cred you can put a 'link' ecu sticker on the whale penis, even though you probably don't have one. You will get the cool sound your after. Please keep the factory air box for a future owner who wants to swap it out or when you realize it is stupid.

In most cases you cannot beat the factory intake setup. Just put a new air filter in the factory box. I did recently and definitely noticed an increase in power, also got some induction noise at high rpm. You cannot hear the induction noise outside the car when revving up to 4000 rpm between speed bumps on the main street but that doesn't matter because I don't intend on looking like a ****** and all those school aged car sl*ts are too young for me now.

Love it Tim. But calm down, I'm not 0-speed hump guy! I was just asking opinions! I will try the piper cross replacement filter I think based on your sound (albeit bit of a rant) advice.

If you take a look at my pic you'll see my car is quite original...

Thanks for your input though will not swap out the original box, any tips on making look a bit better though, ie cleaning it up? Things are looking pretty good under the bonnet as I've replaced a lot of pipes and parts recently.

Depending on how much work you want to do - gasket match the inlet and exhaust tracts; headers; larger bore exhaust; street cam; port the heads (head off for the last one). After that it gets REAL expensive. How much power do you want to spend?

I think I'd like to try and get it to around 130-140bhp, just give it a little extra. How much does cam upgrade cost? It has s/s exhaust (whole system), I think I need to get the interior finished and see what kind of money I have to play with....

I can't see cam change being less than £200......

I've got the blower motor to sort next.

Rear seats being retrimmed, need to order a dash cap or find second hand one.

Ive read quite a few people try and build the M40 engine on bimmersport.co.nz and only result ive ever seen is running it on mild boost. pretty much anything else you throw at it won't do anything.

My advise if you want to start chasing power is convert it to an M42 and go from there.

but none wants to hear a DOHC 4 cylinder with a big bore exhaust any more than they want to hear a SOHCer.

with that said though 130-140hp is only around 20hp more than stock so a realistic aspriation. i see in the other posts you have made that you are quite good with maintenence.

Alternatively, why not disregard all of this and throw in a shorter diff ratio? that will give you more acceleration and more perceived HP. economy may suffer a bit but its a 1.8L so pretty good already

Seeing that you are in the UK, why not go for a K&N replacement filter and a proper tune by a Unichip dealer ?
I have gotten close to 10 Hp out of some M40 with these mods, others did not respond too well.
The Unichip tuner should not charge you anything, if there is no positive result
the K&N will give you a million mile warranty
These mods should increase performance with a decrease in fool consumption

I've got a piper cross panel filter on the way and will check out the tuning . I think it's safe to say goin forward an m42 swap is going to be the way forward . This car is in excellent condition I think it warrants the expenditure.

I've got a piper cross panel filter on the way and will check out the tuning . I think it's safe to say goin forward an m42 swap is going to be the way forward . This car is in excellent condition I think it warrants the expenditure.

How much would I get for my m40 lump?

not a huge amount of UK people here, and every market is different. you can't give an M40 away in the USA, here they go for around $300 complete if they haven't got the dreaded stuck lifters that is a common problem for this engine, and around 140,000kms. That translates to roughly £100 and 90,000miles but again, every market is different so you may get more or less than that

Will do, ill get in contact during the week, just for extra info, after fitting piper cross panel filter there actually is a difference in pick up that I didnt expect....also a nice little grunt at high revs and after quite a long drive there is cut a lot a small increase in efficiency.

I dont mean to call you out, but that is probably just because the filter is a new one, ie if you replaced it with a brand new OEM one you would get the same result

Fair shout Andy although the oem one was only a month or so old, it's not a massive difference but I did a 200 mile journey and got slightly better economy, also this is the first time since I've had the car that its been running properly!! So I might just be seeing it at its best.

To be honest I'm getting around 30-32mpg it's a manual, that trip was just me and the wife, also I don't drive it hard....they are extremely economical vehicles for the age! There are plenty of 1800's that aren't any better now!

I put a 3" K&N cone "cold air intake" on my 325i and it didn't make a bunch of difference. The sound is a bit better, and it maybe added 3-5 horse. It does look better and is easier to clean. Worth the money, but not a big performance booster.